Implement JSON parsing and HTTP integration tasks

Problem Statement

You are building a service for a geospatial analytics dashboard. You need to read point coordinates from a JSON-formatted string, validate the entries, query an external color-assignment API in batches, and output a mapping of each valid point ID to its assigned hex color.

Task

Implement the class PointColorService with the following method:

class PointColorService:
    def __init__(self, http_client: HttpClient, batch_size: int = 10):
        """
        http_client: An object providing a post(url: str, json_data: dict) -> HttpResponse method.
        batch_size: Maximum number of points to send in a single HTTP request.
        """
        pass

    def assign_colors(self, json_payload: str) -> dict[str, str]:
        """
        Parses points from json_payload, fetches color codes via http_client,
        and returns a dict mapping point_id -> hex_color.
        """
        pass

Specifications

1. Input JSON Format: The input string is expected to parse into a dictionary containing a "points" list:

   {
     "points": [
       {"id": "pt_1", "x": 12.5, "y": -4.2},
       {"id": "pt_2", "x": 0.0, "y": 15.1}
     ]
   }
   

   • Points with missing id, x, or y, non-string id, or non-numeric x/y values are invalid and must be skipped.
   • If the JSON itself is malformed or not a valid object with a list under "points", return an empty dictionary {}.

2. HTTP Integration:

   • For every batch of up to batch_size valid points, make a POST request to "/api/v1/colors/resolve" using http_client.post(url, json_data).
   • Payload structure: {"items": [{"id": "...", "x": ..., "y": ...}, ...]}.
   • The response object HttpResponse has fields: status_code: int and body: dict.
   • On success (status_code == 200), body is structured as {"colors": [{"id": "...", "color": "#RRGGBB"}, ...]}.
   • If an HTTP call fails (status_code != 200 or an exception occurs), assign a fallback color "#000000" to all points in that batch.

3. Output Format:

   • Return a dictionary mapping point_id to its resolved hex color string (e.g. {"pt_1": "#FF5733", "pt_2": "#33FF57"}).

Constraints

• 0 <= number of points <= 10,000
• 1 <= batch_size <= 500
• Point IDs within a valid payload are unique.

Example

# Input payload
payload = '''{
  "points": [
    {"id": "p1", "x": 1.0, "y": 2.0},
    {"id": "p2", "x": 3.0, "y": "invalid"},
    {"id": "p3", "x": -1.0, "y": 0.0}
  ]
}'''

# Assuming batch_size=2 and http_client returns:
# POST /api/v1/colors/resolve with items [p1, p3] -> status 200, 
# body: {"colors": [{"id": "p1", "color": "#FF0000"}, {"id": "p3", "color": "#0000FF"}]}

service = PointColorService(http_client, batch_size=2)
result = service.assign_colors(payload)
# result == {"p1": "#FF0000", "p3": "#0000FF"}